1. Field of the Invention
The present invention relates to a disc-molding mold for molding discs.
2. Description of the Related Art
Conventionally, in an injection molding machine for molding disc substrates, resin heated and melted within a heating cylinder is charged into a cavity formed in a disc-molding mold. The molten resin is cooled and solidified within the cavity to thereby obtain a molded disc substrate.
FIG. 1 is a sectional view of a conventional disc-molding mold.
In FIG. 1, a stationary-side mold assembly 12 is fixed to an unillustrated stationary platen by use of unillustrated bolts. The stationary-side mold assembly 12 includes a base plate 15; a disc plate 16 fixed to the base plate 15 by use of bolts 17; a locating ring 23 disposed on the base plate 15 in such a manner as to face the stationary platen and adapted to position the base plate 15 with respect to the stationary platen; and a sprue bushing 24 disposed adjacent to the locating ring 23. A front end (the left end in FIG. 1) of the sprue bushing 24 faces a cavity C, and a die 28 is formed in the front end of the sprue bushing 24. In communication with the die 28, a sprue 26 is formed in the sprue bushing 24 in order to allow passage of resin injected from an injection nozzle of an unillustrated injection unit.
A movable-side mold assembly 32 is attached to an unillustrated movable platen by use of unillustrated bolts. The movable-side mold assembly 32 includes a base plate 35; an intermediate plate 40 attached to the base plate 35 by use of bolts 37; a disc plate 36 attached to the intermediate plate 40 by use of bolts 42; a cylinder 44 which is disposed within the base plate 35 in such a manner as to face the movable platen and which is attached to the intermediate plate 40 by use of bolts 45; and a cut punch 48 which advances and retracts (moves rightward and leftward in FIG. 1) along the cylinder 44 and which has a shape corresponding to the die 28.
A depression is formed on the surface of the disc plate 36 facing the disc plate 16, in order to define the cavity C. When the movable platen is moved toward the stationary platen through operation of an unillustrated mold clamping apparatus to thereby perform mold closing and mold clamping, the disc plate 36 is pressed against the disc plate 16 to thereby form the cavity C therebetween.
A flange 51 integrally formed with the cut punch 48 is disposed within the cylinder 44 such that it can advance and retract. The rear end (the left end in FIG. 1) of the flange 51 is received by the cylinder 44. A cut-punch return spring 52 is disposed on the front side (on the right side in FIG. 1) of the flange 51. The cut-punch return spring 52 urges the flange 51 rearward (leftward in FIG. 1).
When, in the mold-closed state, the flange 51 is advanced (moved rightward in FIG. 1) through feed of oil to an unillustrated drive cylinder, the cut punch 48 is advanced and enters the die 28. As a result, a hole is punched in an unillustrated disc substrate of resin molded within the cavity C.
Meanwhile, the mold assemblies 12 and 32 are aligned with each other by means of guide posts 54. Four guide post holes 53 (two of which are shown in FIG. 1) are formed in the base plate 15 through grinding such that they are arranged on a concentric circle relative to the center of the mold assembly 12. The guide posts 54 are press-fitted into the corresponding guide post holes 53 in such a manner as to project toward the mold assembly 32. Furthermore, the guide posts 54 are fixed to the base plate 15 by use of corresponding bolts 55.
Guide bushing holes 56 are formed through grinding in the intermediate plate 40 at positions corresponding to the guide post holes 53. Guide bushings 57 are press-fitted into the corresponding guide bushing holes 56. The guide bushings 57 guide the corresponding guide posts 54. During mold closing, the guide posts 54 enter the corresponding guide holes formed in the guide bushings 57 via unillustrated ball bearing portions of the guide bushings 57, whereby the mold assemblies 12 and 32 are aligned with each other.
Temperature control medium passages 61 and 62 are formed in the disc plates 16 and 36, respectively. A medium, such as water, oil, or air, is fed into the temperature control medium passages 61 and 62 so as to cool the disc plates 16 and 36, respectively.
However, the conventional disc-molding mold involves the following problem. As resin injected from an injection nozzle passes through the sprue 26 and is charged into the cavity C, a difference in thermal expansion arises between the mold assembly 32 and the mold assembly 12. Specifically, in the mold assembly 32, heat of resin contained in the cavity C is transmitted to the guide bushings 57 via the disc plate 36 and the intermediate plate 40. In the mold assembly 12, not only is the heat transmitted to the guide posts 54 via the disc plate 16 and the base plate 15, but also heat of resin passing through the sprue 26 is transmitted to the guide posts 54 via the sprue bushing 24 and the base plate 15. Thus, a difference in thermal expansion arises between the guide bushings 57 and the guide posts 54. As a result, the guide posts 54 may fail to smoothly enter the corresponding guide holes, resulting in a failure to reliably align the mold assemblies 12 and 32 with each other or resulting in galling of a guide post 54.
An object of the present invention is to solve the above-mentioned problem in the conventional disc-molding mold and to provide a disc-molding mold capable of reliably aligning a stationary-side mold assembly and a movable-side mold assembly with each other and preventing galling of a guide post.
To achieve the above object, the present invention provides a disc-molding mold, comprising a first support plate disposed at a stationary side of the mold; a first mirror-surface disc attached to the first support plate; a first guide ring disposed radially outside the first mirror-surface disc and attached to the first support plate; a second support plate disposed at a movable side of the mold; a second mirror-surface disc attached to the second support plate; a second guide ring disposed radially outside the second mirror-surface disc and attached to the second support plate; a guide post attached to either the first or second guide ring and projecting towards the other guide ring; and a guide bushing attached to the other guide ring and adapted to guide the guide post.
The first and second guide rings each have a temperature control medium passage formed therein in order to allow passage of a temperature control medium.
Since a temperature control medium flows through the temperature control medium passages formed in the first and second guide rings, the first and second guide rings are equal in thermal expansion. Thus, the guide post can smoothly enter a guide hole formed in the guide bushing , whereby the mold assemblies can be reliably aligned with each other, and galling of the guide post can be prevented.
The temperature control medium passages can be formed in the first and second guide rings more easily than in the first and second support plates, thereby lowering manufacturing cost of the disc-molding mold.
Preferably, the guide post is positioned with respect to the guide ring to which the guide post is to be attached.
Preferably, a guide post hole is formed in the guide ring to which the guide post is to be attached. The guide post is press-fitted into the guide post hole.
Preferably, the guide bushing is positioned with respect to the other guide ring.
Preferably, a guide bushing hole is formed in the other guide ring. The guide bushing is press-fitted into the guide bushing hole.
Preferably, a ball bearing portion is formed on an outer circumferential surface of the guide post in order to enhance sliding performance between the guide bushing and the guide post.
Preferably, the first and second mirror-surface discs each have a temperature control medium passage formed therein in order to allow passage of a temperature control medium.
Preferably, a guide bushing reception hole is formed in the second support plate in order to allow insertion of the guide bushing into the second support plate. A temperature control medium passage adapted to allow passage of a temperature control medium is formed in the second support plate such that the passage assumes the form of a groove extending on the wall of the guide bushing reception hole.
Preferably, a temperature control medium passage adapted to allow passage of a temperature control medium is formed in the guide bushing such that the passage assumes the form of a groove extending on the outer circumferential surface of the guide bushing.
Preferably, a temperature control medium passage adapted to allow passage of a temperature control medium is formed within the guide post.